1. Field of the Invention
The subject invention is directed to check valves for use in ultra high purity gas flow environments.
2. Description of the Prior Art
The prior art check valve includes a valve housing that is formed or machined to define a valve chamber. The valve housing further is formed or machined to include an inlet extending from an external location into the valve chamber and an outlet extending from the valve chamber to a second external location. Portions of the valve housing that surround the inlet to the valve chamber are configured to define a valve seat. The prior art check valve further includes a valving element that is configured to sealingly engage the valve seat for blocking flow into the valve chamber. On the other hand, the valving element can move away from the valve seat to permit flow from the inlet into the valve chamber.
The prior art check valve further includes a biasing member that urges the valving element into sealing engagement with the valve seat. Thus, the prior art check valve assumes a normally closed position. However, the valving element of the prior art check valve will move away from the valve seat and into its open position if forces exerted by fluid pressure in the inlet exceed the forces exerted by the biasing member. Prior art check valves often are used in situations where it is necessary to prevent contaminants generated at downstream locations from flowing through an unpressurized line and into an upstream location.
Many industrial processes require a very pure flow of a specified gas. Check valves used in these environments must prevent ambient air from flowing into the valve chamber from the surrounding environment. The valve chamber can be sealed securely by welding the components of the prior art valve housing entirely around their engaged faces. However the heat generated during welding can affect the performance and life of the biasing member. Additionally, contaminants from the weldment can leach into the valve.
Many prior art check valves employ a disk-shaped valving element that is intended to be moved in directions substantially along the axis of symmetry of the disk. It has been found that disk-shaped valving elements of these prior art check valves generate a very bothersome noise for a considerable period of time following the opening of the valve. The noise is believed to be attributable to a fluttering of the disk-shaped valving element in the valve chamber of the prior art check valve.
It is desirable to have check valves that respond quickly to fluid pressure in the inlet. However, it is also desirable to have sufficient strong forces exerted by the biasing member of the prior art check valve to ensure secure sealing. These seemingly opposed objectives typically have been resolved in favor of the sealing forces. Thus, many prior art check valves provide relative slow opening responses.
In view of the above, it is an object of the subject invention to provide a check valve that is well suited for use in ultra high purity gas flow environments.
It is another object of the subject invention to provide a check valve that avoids generating noise during and after opening.
It is a further object of the subject invention to provide a check valve that provides secure sealing of the inlet while still permitting a desirably quick opening response.
The subject invention is directed to a check valve having a valve housing formed from a first housing component and a second housing component. The first housing component is configured to define an inlet to the valve and a portion of a valve chamber. The second housing component is configured to define an outlet from the valve and a portion from the valve chamber. The first and second housing components are mateable with one another to define an enclosed valve chamber that communicates only with the inlet to the valve and the outlet from the valve. Mating portions of the first housing component and second housing component may be configured to telescope with one another, and the end of the outer telescoped housing component may be welded to the inner telescoped housing component. The weldment securely seals the valve chamber from the ambient environment, while the location of the weldment substantially prevents contaminants from the weldment teaching into the valve chamber.
Portions of the second housing component may be formed or machined to define a plurality of gas flow channels substantially at an interface region between the valve chamber and the valve outlet. The gas flow channels in the second housing component substantially prevent the valving element described below from blocking the valve outlet.
The check valve of the subject invention further includes a substantially disk-shaped valving element movably disposed in the valve chamber. The valving element is configured to sealingly engage the valve seat that surrounds the inlet to the valve chamber for substantially preventing a flow of gas through the valve. For this purpose, the valving element may include a sealing face to which a seal ring is mounted for sealing engagement with the valve seat. The valving element defines an outer periphery that is dimensioned and/or configured to permit a flow of gas around the valving element when the valving element is spaced from its sealing engagement with the valve seat. More particularly, the valve chamber may include a substantially cylindrically generated inner surface, and the valving element may have a cylindrically generated outer surface that is sufficiently smaller than the cylindrically generated inner surface of the valve chamber to permit gas flow there between. Alternatively, the valve housing and/or the valving element may be configured to define gas flow channels for accommodating a flow of gas when the valving element is spaced from its sealing engagement around the inlet to the valve.
The check valve of the subject invention further includes a substantially disk-shaped spring extending between the valving element and the valve housing. The spring is configured and disposed for urging the valving element toward and into sealing engagement with the valve seat. The spring may be a substantially planar disk that is stamped, machined and/or formed to define a plurality of legs extending between portions of the spring that are connected to the valving element and portions of the spring that are connected to the valve housing. Regions of the spring between the legs accommodate a flow of gas from the inlet to the outlet when the valving element is spaced from its sealing engagement with the valve seat. The legs of the spring preferably extend in non-radially directions, and may include portions that extend substantially helically. Thus, radially inner and radially outer portions of the spring are easily deflectable relative to one another.
The legs of the disk-like spring preferably are non-symmetrically spaced around the axis of the spring. For example, the spring may include two legs that extend from inner or outer locations on the spring that are spaced from one another by approximately 120xc2x0. Thus, a large arc segment of the spring will exist without legs extending between the valving element and the valve housing. This configuration results in an asymmetrical or non-uniform application of forces exerted by the spring between the valve housing and the valving element. These non-uniform forces substantially prevent the generation of a resonant condition in the valving element that would cause a noise-generating flutter in the valving element. As a result, the valve of the subject invention is substantially quieter than prior art check valves and leads to a substantially improved work environment. Additionally, the non-symmetrical loading achieved by the spring causes one side of the spring to initially lift from sealing engagement from the valve housing. Other parts of the spring then rapidly follow the initial movement of the valving element from sealing engagement. This characteristic is roughly comparable to separating a suction cup from a surface by initially lifting one side of the suction cup rather than pulling the suction cup axially. Consequently, the spring employed in the subject check valve results in a very rapid opening response.
Central portions of the disk-like spring may be connected to the valving element, and outer portions of the disk-like spring may be connected to the valve housing. More particularly, central portions of the spring may be securely affixed between two components of the valving element that are staked together near the longitudinal axis of the valving element. Similarly, outer portions of the spring may be secured between the first and second housing components. This configuration and disposition of the spring relative to the valving element and to the housing components is conducive to the above-described asymmetrical configuration of the spring and the above-referenced advantages thereof. Additionally, this dispositioning of the spring enables the spring to be isolated from the heat of welding, as explained herein.
In use, the spring urges the valving element into a normally closed in which the valving element sealingly engages the valve seat. Pressurized gas directed into the inlet of the valve housing will exert forces on the sealing face of the valving element. Sufficient forces exerted by gases in the inlet will overcome the forces exerted by the spring. However, due to the non-symmetrical nature of the spring, these gas forces will cause one side of the valving element to lift away from sealing engagement with the valve seat. Other portions of the valving element will follow quickly, and the valving element will move away from the inlet and into a fully opened condition. The asymmetrical forces exerted by the spring will prevent the establishment of a resonant condition that would cause a rocking or fluttering of the valving element in the chamber and that would generate an objectionable noise. The movement of the valving element in the opening direction may extend until the valving element engages portions of the second housing component surrounding the outlet to the valve. However, channels formed in the second housing component prevent a complete blockage of the outlet and ensure a continuous flow of gas between the axially aligned inlet and outlet. Upon termination or significant reduction of the gas flow toward the inlet, the spring will urge the valving element back into sealing engagement with the valve housing. The asymmetrical configuration of the spring may cause one side of the valving element to contact the valve housing initially. However, remaining portions of the valving element will move quickly into complete sealing engagement with the valve housing.